How Can the Merit of Spiritual Practice Not Be in Vain?

Being able to read, contemplate, and work with single-minded focus is all the mind consciousness's meditative concentration (samādhi). But if the manas is not interested in this, is not concentrated on reading and working, and does not attentively focus on the content of the book, can the mind consciousness still be concentrated? Absolutely impossible. If the manas is not concentrated, the six consciousnesses cannot hope to be concentrated; the six consciousnesses will inevitably be scattered and restless like monkeys. Even though the mind consciousness constantly focuses its attention, it is of no use—it will still be dragged around everywhere by the manas. Therefore, subduing the manas is an extremely crucial point in cultivation. Hearing, contemplation, practice, and realization must all be implemented upon the manas in order for the effort not to be in vain, and there will surely be results and karmic retribution.